This is a simple circuit showing two mismatched
transmission
lines. The first line is 75 ohms, and the second line is 500 ohms. Waves
traveling down the first line are reflected at the boundary, causing a
standing
wave on the line, which is a wave that oscillates but does not appear to
travel. It is actually the combination of two waves (the initial wave,
and the reflected wave) traveling in opposite directions.

The second line is properly terminated, so there are no reflections on that one.